Anabolic-androgenic steroids (AAS) are an increasingly popular substance of abuse among adolescents, as well as elite athletes. The actions of AAS in the central nervous system are poorly understood, however, recent studies in rodents indicate that AAS induce rapid and reversible modulation of gamma-aminobutyric acid type A (GABAA) receptor-mediated currents in neurons of forebrain regions of both prepubertal and adult animals. Moreover, the ability of AAS to modulate currents in the forebrain is region- specific and depends on receptor subunit composition. The expression of GABAA receptors comprising different subunit isoforms is heterogeneous throughout the brain and regulated both in a region-specific and developmental manner. Therefore, understanding differential AAS modulation of GABAA receptors composed of different subunits establishes the essential groundwork for understanding the actions of AAS in the central nervous system. The cerebellum is an ideal system for allosteric modulation of GABAA receptors because the cell-specific patterns of expression of different subunits and the functional modulation of GABAA receptor-mediated currents by other modulators have been well characterized, especially in Purkinje and granule cells. In addition, the cerebellum is the essential structure in mediating motor memory and motor coordination, both of which may be affected during AAS. Using whole-cell patch-clamp recording techniques of neurons in acutely isolated brain slices, the ability of specific AAS to induce different patterns of modulation upon inhibitory postsynaptic currents (IPSCs) in Purkinje cells and granule cells of postnatal rats will be determined. Second, to correlate, at the single cell level, significant differences in the ability of AAS to modulate GABAergic IPSCs with cell-specific patterns of subunit gene expression, single cell RT-PCR will be used to detect the ratio of subunit families expressed. Finally, using ultrafast perfusion patch-clamp technique on recombinant GABAA receptors expressed in transfected cells, the subunit dependence of AAS IPSC modulation will be determined.